another animated series to look out for: "Blue-eye Samurai"

I left a comment beneath the video, though:

If you remember back to Punnett squares in biology class, you may recall that blue eyes come from recessive genes. If a blue-eyed man fathers a child with a full-blooded Japanese woman, there's a 0% chance the child will have blue eyes: she will be brown-eye dominant. If the child grows up and meets another brown-eye dominant man, they can have a blue-eyed child. In the language of the Punnett square, pure brown eyes (BB) crossed with pure blue eyes (bb) will always result in Bb children—brown-eye dominant, 0% blue eyes. But if Bb meets another Bb, there is a 25% chance of having a blue-eyed child. I haven't watched this series and don't know the story, but it seems to me that a first-generation blue-eyed protagonist is impossible. Is she, perhaps, second-generation? Or is her Japanese mother only half-Japanese and therefore Bb? If the latter, then there's a 50% chance of blue-eyed progeny.